Cellulose chirality

由于纤维素在植物细胞壁中无处不在的结构作用，作为一种丰富的、可再生的、碳中性和无毒的材料，有助于增强木材、纸张、纺织品和纳米复合材料的强度，纤维素的研究已经复兴。我们计划将重点放在一种被忽视的纤维素性质上，即它的手性。手性是在几个长度尺度上表示的。当然，单个葡萄糖单元包含手性碳中心，但在较长的尺度上，这种手性也影响纤维素的晶体结构，以及植物细胞壁、纸浆纤维、纸张和木材的超结构。文艺复兴的一个方面是世界范围内对各种形式的纳米纤维素的兴趣(今年我们的研究在这个领域获得了很多认可)。但仍有几个尚未开发的更大规模的研究领域，我们希望在这项提案中加以解决。**多年来，我们首次观察到了几种纤维素材料的手性结构和响应。我们计划将重点放在两个特别的观察上。首先，我们发现纤维素纳米晶的有序胶体悬浮液形成了左旋手性向列结构，这意味着棒状纳米晶之间存在一定的手性相互作用。我们和其他人已经对这种相互作用的性质进行了推测，但缺乏实验证据。我们希望应用AFM力测量来直接解决这个问题。纤维素样品的选择和仪器的几何形状将是关键变量。**第二，我们首次从许多植物的叶柄(叶茎)中分离出一种右旋卷曲的纤维素基结构。目前尚不清楚这种利手性是纤维素微纤维手性相互作用的结果，还是生物合成途径的结果(或两者兼而有之)。无论如何，观察到的结构似乎在植物维管系统的水分运输中发挥了作用。虽然植物的维管系统已经得到了广泛的研究，但关于这一关键的自然过程仍然存在许多问题。我们想从物理化学的角度来检验我们对叶柄结构和功能的初步观察的意义。

There has been a renaissance in cellulose research, based on its ubiquitous structural role in the plant cell wall, its value as an abundant, renewable, carbon-neutral and non-toxic material that contributes to the strength of wood, paper, textiles and nanocomposites. We plan to focus on one neglected cellulose property, namely its chirality. The chirality is expressed over several length scales. Of course, the individual glucose units contain chiral carbon centres, but at longer length scales, this chirality also influences the crystalline structure of cellulose, and the superstructure of plant cell walls, pulp fibres, paper and wood. One aspect of the renaissance has been the world-wide interest in various forms of nanocellulose (a field where our research has garnered a lot of recognition this year). But there remain several untapped areas of research at larger length scales that we would like to address in this proposal. **Over the years, we have observed, for the first time, the chiral structure and response of several cellulosic materials. We plan to focus on two particular observations. First, we found that ordered colloidal suspensions of cellulose nanocrystals form a left-handed chiral nematic structure, implying that there is some chiral interaction between the rod-like nanocrystals. We and others have speculated about the nature of this interaction, but experimental evidence is lacking. We hope to apply AFM force measurements to address this problem directly. Choice of cellulose samples and instrument geometries will be the key variables. **Second, we've isolated for the first time a right-handed coiled cellulose-based structure from the petioles (leaf-stems) of many plants. Whether the handedness is a function of the chiral interactions of cellulose microfibrils, or is a result of biosynthetic pathways (or both) is unclear. In any case, the observed structures would seem to play a role in water transport through the plant vascular system. While the vascular system of plants has been extensively investigated, many questions on this key natural process remain. We would like to examine the significance of our preliminary observations on petiole structure and function from a physico-chemical viewpoint.